Long term manual wheelchair users are at high risk of upper-limb injuries due to high repetitive loads applied to the upper limbs. [1] [2]
To reduce this impact a novel manual wheelchair propulsion device was developed based on a dynamically optimized handle based propulsion movement developed by Kurup et. al. [3]
Starting point was the prescribed propulsion path with 0.89 circularity ratio which was realized as a sliding guide for the handle mounted at the side of a conventional wheelchair instead of the armrest. A crank is mounted at the centre of the path and during the rotation it follows the sliding guide by adapting the crank length. With timing belts the propulsion is transmitted from the handle to the back wheel. A special pulley layout allows easy adaptation of the crank centre position to the individual userīs anthropometric size.
The novel hand propulsion device was mounted on a wheelchair based test rig that generates adjustable resistance power. With a force measurement handle the applied forces during the exercise were captured. Also the geometrical data were recorded with a motion capturing system.
First tests with three healthy subjects at 30 Watt resistance have shown an effective force component (FEF) at the handle of 79% in comparison to up to 75% for conventional pushrim propulsion. [4]
Currently, shape design and drivetrain are optimized to further increase the efficiency of the hand propulsion device. Next step will be tests on a group of long term wheelchair users to confirm the potential of this development.